Bonded tendons have been used in heavy-water reactor containment buildings and some light-water reactor containment buildings in Korean nuclear power plants, and evaluation of prestressing forces of the bonded tendons is important for evaluating the structural integrity of the containment buildings. In Korean Wolsug Nuclear Power Plant units 1 to 4 and Uljin Nuclear Power Plant units 1 and 2, bonded tendons have been used in a method of filling the insides of sheathing pipes surrounding the bonded tendons with cement grout.
Particularly, prestressing forces of bonded tendons of a heavy-water reactor type nuclear power plant are indirectly evaluated during reactor operations, by performing a bending test, a destructive test, and a lift-off test using test beams manufactured at the time of nuclear power plant construction. However, since such an indirect evaluation method is ineffective in terms of reliability and economic aspects, the development of direct and practicable methods of estimating prestressing forces of bonded tendons is urgently required.
Methods for estimating prestressing forces of bonded tendons have not been researched, and published methods for estimating prestressing forces of tendons are mainly for unbounded tendons. In addition, most major domestic (Korean) bridges have been constructed using bonded tendons, and evaluation of load bearing capacities and remaining life span of these bridges is an important pending issue. In evaluations of the load bearing capacities and remaining life span of bridges, prestressing forces of bonded tendons are important factors. Therefore, the development of technology for estimating prestressing forces of bonded tendons is considered to be a very urgent and important task.